Automatically disabled backspace mechanism



L. E. HARE March 11, 1969 AUTOMATICALLY DISABLED BACKSPACE MECHANISMSheet Filed Sept. 29, 1966 pi\ Qmmmk; a I

Fly-1 INVENTOR LLOYD E. HARE ATTORNEY March 11, 1969 HARE 3,432,019

AUTOMATICALLY DISABLED BACKSPACE MECHANISM Filed Sept. 29, 1966 B Fig-2Sheet 2 OfZ LLOYD E. HARE INVENTOR 54 77 76 BY 7 iii/ V ATTORNEY UnitedStates Patent 1 Claim ABSTRACT OF THE DISCLOSURE In a conventionalcarriage typewriter, a power operated backspace mechanism having abackspace pawl, is provided with an interposer responsive to movement ofthe carriage to a left margin position to block engagement of thebackspace pawl with a carriage rack while permitting translatorymovement of the pawl should a backspace key lever be depressed with thecarriage so positioned.

This invention relates to a power operated backspace mechanism fortypewriters or like machines; more particularly it relates to backspacemechanism disabling elements responsive to movement of the typewritercarriage to a left hand margin position to render the backspacemechanism ineffective to move the carriage as long as the carriage islocated at said left hand margin position.

In a known typewriter, a backspace pawl is power driven into engagementwith and translates a rack on the carriage incident to each backspacingoperation. In such a mechanism the initiation of a backspace operation,when the carriage is located at a preset left margin position, jogs thecarriage causing the left margin locator and a frame supported post topound against one another as the carriage is power driven toward anddrawn back from the center post incident to each backspace operation.The noise and vibration incident to this jogging is not only irritatingto a typist but more importantly, harmful to the mechanism.

In accordance with the present invention there is provided mechanismeffective to prevent jogging of the can riage incident to a backspaceoperation called after the carriage has movedto a preset or final leftmargin position. More particularly there is provided interposermechanism responsive to movement of the carriage to a left marginposition to block engagement of the backspace pawl with the rack whileyet permitting translatory movement of the pawl should a backspace keylever be depressed with the carriage so positioned.

An object of the invention is to provide backspace mechanism disablingelements to prevent carriage movement incident to backspace operationsinitiated after the carriage has been moved to a left hand marginposition.

Another object of the invention is in the provision of backspacemechanism disconnect elements positionable when the typewriter carriagehas moved to a left hand margin limit to prevent engagement and movementof the carriage by power operated backspace mechanism.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing in which like referencenumerals designate like parts throughout the figures thereof andwherein:

FIGURE 1 is a perspective view, looking from the rear of the typewriter,of backspace mechanism and an associated disconnect element orinterposer in accordance with the invention;

FIGURE 2 is a perspective view, looking from the front of thetypewriter, showing the operative relationship of the interposer withframe and carriage supported elements;

FIGURE 3 is a partial elevational view showing the inactive position ofthe interposer;

FIGURE 4 is a view similar to FIGURE 3 showing an intermediate inactiveposition of the interposer; and

FIGURE 5 is a view similar to FIGURE 3 showing the active position ofthe interposer.

Referring now to the drawing wherein like reference characters designatelike or corresponding elements throughout the several views there isshown in FIGURE 1 a typewriter carriage supported feed rack 10 which isadapted to be moved in a letter feed direction indicated by arrow 11 bya spring motor connected to the carriage by a drawband under control ofan escapement generally designated by reference numeral 12. The carriagesupported feed rack 10 is adapted to be indexed in a backspace directionindicated by arrow 13 by a pawl generally designated by referencenumeral 14 which when actuated moves upwardly into rack engagement andthen translates to move the carriage supported feed rack 10 in thedirection of arrow 13.

Actuation of the backspace pawl 14 is effected by depression of abackspaced key lever 15 whose rear end is formed with upper and lowerlongitudinally offset stop lugs 16 and 17. The upper and shorter lug 16normally lies in the wrap path of the axially bent end 18 of a radiallyoffset coil spring 21 of a conventional wrap spring clutch generallydesignated by reference numeral 21a to maintain the clutch disengaged.The wrap spring clutch 21a comprises a constantly rotating shaft orsleeve 19 surrounded by the coil spring 21 with the other end of thecoil spring 21 secured to the output element 22 of the wrap springclutch 21a which takes the form of a cam. A clutch cycle is effected byraising the lug 16 from the offset spring end 1'8 allowing the spring 21to wrap and couple the shaft 19 and cam 22. The clutch will bedisengaged at the end of a revolution by the upper or lower stop lug;the latter if the lever 15 is still raised after a revolution. When suchis the case, upon return of the lever 15 to normal the spring end 18will be caught by the upper lug 16 before the spring 21 can wrap. Repeatactions are effected by raising both lugs 16 and 17 from the path of end18. i i

A cam follower arm 23, pivotally mounted to a machine frame member 24 atone end 25, is provided intermediate its ends with a dependingprojection 26 which rotatably supports a roller 27 adapted to roll aboutthe cam periphery. The other end of the cam follower arm 23 isarticulately connected to a vertical thrust link 28 whose upperextremity is bent over and to which is secured a threaded stud 29. Thestud 29 supports a stroke or pitch adjusting nut 31 having a roundedcrown and further extends through an opening of larger diameter than thestud 29, provided in a bent off part 33 of a lateral arm 34 of a pawllift crank 35. The underside of the part 33 of pawl lift crank 35 isshaped complimentary to and resiliently held against the rounded crownof pitch adjusting nut 31 by a spring 36 trapped between a washer 32resting on the crank arm 34 and a nut 3111. Thus the pawl lift crank 35is articulately connected to the vertical thrust link 28 by a relativelyfrictionless pivot. The pawl lift crank 35 is pivotally supported on aframe supported stud 37. Also pivotally mounted on the frame supportedstud 37 is a vertically extending swing arm 38 whose upper end ispivotally connected as at 39 to one end of the backspace pawl 14. Asshown in FIGURE 1 the backspace pawl 14 has a depending part 41 whichlies in the path of the vertically extending arm 42 of the pawl liftcrank 35. The backspace pawl 14 extends leftwardly from the pivot 39 andits left end is bifurcated to provide upper and lower arms 43 and 44,respectively, laterally offset from one another to embrace a framesupported guide plate 45. The upper arm 43 is formed with a verticallyextending tooth 46 adapted to engage and move the carriage feed rack aswill presently appear. Both the upper and lower arms 43 and 44 areprovided with pins 47 and 48 respectively, extending rearwardly. The pin47 on the upper arm 43 extends into a substantially rectangular cutout49 in the guide plate 45 whose right edge 51 slants upwardly andleftwardly. Normally the pawl 14 and swing arm 38 are held to the rightby a return spring 52 connected to the lower pin 48 and an ear 53 on theframe supported guide plate 45 so that the upper pin 47 is locatedadjacent the lower right hand corner of the guide plate cutout 49.

When the clutch is cycled by depression of the backspace key lever 15,the thrust lever 28 rocks the pawl lift crank 35 counterclockwise aboutpivot 37 whereby its upper arm 42 engages the depending part 41 of pawl14 to rock the pawl 14 clockwise about its pivot connection 39 to theswing arm 38 to elevate the pawl tooth 46 along the slanted edge 51 intorack engagement; the return spring 52 preventing translation of the pawl14 (and rotation of swing arm 38) to the left until the pin 47 reachesthe top of the cutout 49 which limits further elevation. The continuedapplication of torque by the pawl lift crank 35 to the pawl 14 after thepawl tooth 46 engages the carriage supported feed rack 10 will overcomethe force of spring 52 allowing the swing arm 38 to pivot about pivot 37and pawl 14 to translate to the left and carry the carriage supportedfeed rack 10 in the direction of arrow 13. The hereinabove describedbackspace mechanism is similar in material respects to that disclosed inPatent No. 2,577,467.

As will be understood the movement of the typewriter carriage in abackspace or carriage return direction indicated by arrow 13 in FIGURES1 and 2 is limited by a frame supported centerpost 54 located in thepath of an abutment screw 55 (FIGURES 35) on a conventional margin stopgenerally designated by reference numeral 56 (FIGURE 2) which ispositionable along a margin rack 57 supported by the carriage rearwardlyof the carriage supported feed rack 10. Pivotally mounted on thecenterpost 54 is a carriage return clutch knock-off paddle 58 which isrocked against the centerpost 54 when the abutment screw 55 is movedtoward the centerpost 54. The margin stop 56 includes a depending catch59 adapted when the carriage is, in the embodiment disclosed,approximately 5 spaces from its left hand margin to engage and pull inthe direction of arrow 13 a U-shaped end 60 of a lever 61 whose otherend 62 is pivotally mounted on a dashpot actuator slide 63 supported forlateral movement as by pins 64 extending from a machine frame supportedcross rail 65 into slots 66 thereof.

A depending arm 67 of the dashpot actuator slide 63 is secured to theplunger 68 of a dashpot (not shown) which as is understood is operativeto dissipate the relatively high energy potential of a fast movingcarriage over the 5 space interval, thus decelerating the carriage aftera relatively long carriage return run before its movement is terminatedby the centerpost 54. During backspacing operations through said 5spaces, however. the dashpot offers negligible impedance.

The movement of the dashpot actuator slide 63 is employed in accordancewith the present invention to control the movement of a backspace pawldisabling lever or interposer generally designated by reference numeral71. It is to be understood however that the dashpot actuator slide 63 isemployed to control interposer 71 merely because it exists in aconventional machine and that a separate lever responsive to carragemovement through its final increments or increment of movement could beemployed to so control the interposer 71.

As viewed in FIGURE 2 the interposer 71 is pivotally mounted between itsends on a frame supported pin 72. The extremity of the generallyrearwardly extending arm 73 of the interposer 71 is bent back slightlyforwardly whereby the bend 74 normally rests on the face of thedepending part 67 of the dashpot actuator slide 63. The generallyforwardly extending arm 75 has an end 76 adapted to move over and blockthe upward movement of the pin 48 on the lower arm 44 of the pawl 14. Asshown in dotted outline in FIGURE 2 the elevated position of the pin 48lies in the horizontal plane through which the fiat end 76 of theinterposer 71 moves. A spring 77 secured to the forwardly extending armand to the machine frame is operative to move the interposer 71clockwise from the normal position, as viewed in FIGURES 2 and 3, as theactuator slide 63 is moved to the right by the carriage mounted marginstop 56. FIGURE 4 shows the position of the interposer with the carriageone increment from the left margin position. If a backspace operation isinitiated at this position, the carriage mounted margin stop will movethe actuator slide 63 further to the right and the interposer 71 will bepositioned over the pin 48 when the final carriage position is reached,as shown in FIGURE 5, in which the margin stop abutment screw 55 isshown against the carriage return knock-off paddle 58. During the lastbackspace increment, as the interposer 71 moves toward a blockingposition, the rising pin 48 will cammingly engage the left edge (FIGURE2-5) of the end 76 thereof, to rock the interposer 71 counterclockwise,and during translation push the interposer 71 into a neutral position tothereby allow the backspace pawl 14 to engage and move the carriagesupported feed rack 10' to its final position. Where the increments ofmovement are less than shown. the interposer 71 will be swung to aneutral position by the pin 48 several times incident to backspacingincrements in advance of the final one. Whatever the pitch of themachine as the last backspace increment is completed, the interposer 71swings over and beyond the axis of the pin 48 precluding any cammingaction and thereby blocking the pin 48.

Prior to the present invention, if a backspace operation were initiatedat the final carriage position, the pawl 14 would engage and move thecarriage causing the margin stop abutment screw 55 to drive the paddle58 toward the centerpost 54 during the power stroke of the backspacemechanism. As this paddle movement is insulficient to permit backspacingmovement over a letter feed increment, on the return stroke of thebackspace mechanism the carriage would be drawn back to the FIGURE 5position by the spring motor. Thus a single or repeat backspace in suchcondition would jog the carriage.

With the present invention, the initiation of a backspace operation withthe interposer 71 positioned above pin 48 as shown in FIGURE 5, the pawl14 is prevented from rising and can only translate; to the left asviewed in FIGURE 1 or to the right as viewed in FIGURES 2-5. Thus thecarriage is not engaged and remains motionless.

In conventional machines there is provided a margin release mechanism topermit carriage movement beyond a preset left margain. Such marginrelease mechanisms are effective to rock the centerpost assembly 54 outof the path of the margin stop abutment screw 55 and to pull the lever61 counterclockwise, thus releasing the margin stop 56 and the dashpotactuator lever 61 permitting the interposer 71 to move out from ablocking position so that backspacing of the carriage through the marginmay be accomplished. The limiting or final carriage position abutmentanda dashpot actuating catch on the carriage frame will be similarlyeifective at the limiting carriage position to preclude movement of thecarriage by the backspacing mechanism.

The invention claimed is:

1. A backspace mechanism for a typewriter comprisa movable carriage;

a carriage supported feed rack;

a pawl;

a keylever actuated power means for driving said pawl whereby whendriven said pawl will normally rock into engagement with said carriagesupported feed rack and then move in a backspace direction to move saidcarriage supported feed rack in a backspace direction;

a carriage supported margin stop;

a frame supported centerpost cooperable with said margain stop fordetermining a left hand margin position for said carriage;

interposer means normally inoperable, movable to an operable positionoverlying a pin extending laterally from said pawl to prevent rockingmovement of said pawl, so that when said pawl is driven by said keyleveractuated power means said pawl will move in a backspace directionwithout first engaging said carriage supported feed rack;

and means responsive to movement of said carriage, for

moving said interposer means to an operable position when said carriagearrives at a left hand margin position determined by said framesupported centerpost and said margin stop, said responsive means holdingsaid interposer means in an operable position as long as said carriageremains in a left hand margin position, thereby preventing jogging ofthe carriage incident to a backspace operation called while the carriageis in a left hand margin position.

References Cited UNITED STATES PATENTS 966,035 8/1910 Mercer 197911,873,553 8/1932 Crumrine l9791 1,955,614 4/1934 Thompson et a1. 19794 X2,088,064 7/1937 Koca 197-91 2,577,467 12/1951 Kloski et a]. 197-912,728,437 12/1955 Kupper 1979l 3,217,850 11/1965 Frechette ct a1. 197-91X ERNEST T. WRIGHT, Primary Examiner.

